The present invention relates generally to torque converters, and more particularly relates to automatic transmissions which may be defined as a device used to transmit power or energy while changing the level of torque.
At present, fluid torque converters dominate the field because of their smoothness, long endurance, and high power transmission capability, but by no means are fluid converters ideal. For example, in the hydrodynamic torque converter, most commonly found in the automobile, the angle of the stator blades does not vary according to the slip ratio. Thus, for any slip ratio greater or less than that which produces tangential flow for the fixed stator blade angle, a loss occurs through hydraulic shock. Due to the rapid fall of efficiency for an increased stator blade angle, planetary automatic shift is required. This complicates the mechanism and decreases the reliability.
The most common mechanical transmission in use today is the sliding gear (standard) transmission which is a very efficient component, but it is incapable of automatically changing the speed ratio without manually changing the gears. Most power sources can operate only over a small speed range with good economy and power. As a result, a large number of gear changes are required for efficient operation (e.g., some large trucks have up to 16 forward gears).
Mechanical torque converters conceived in the 1920's, though potentially more efficient than present automatic transmissions, were not competitive because of their jerkiness and low endurance. Many of the endurance problems encountered were due to the necessary overrunning clutches. Most of the major improvements made on the overrunning clutch came after the general rejection of the earlier mechanical torque converters. This is therefore not a problem in the present mechanism. Also, the problem of jerkiness is greatly reduced in the present mechanism by the use of two or more inertia devices in the proper phase relationship. Thus, the mechanical torque converter of the present invention retains the advantages inherent in an automatic transmission while avoiding limitations of early designs.